Substrate surface metallization method and substrate having metallized surface manufactured by the same

ABSTRACT

A substrate having metallized surface is provided. The substrate having metallized surface includes a silicon substrate, an adhesive layer and a metallic layer. The silicon substrate has a silanated surface and the adhesive layer is disposed on the silanated surface. The metallic layer bonds to the silanated surface through the adhesive layer. The adhesive layer is formed with a plurality of colloidal nanoparticle groups, the colloidal nanoparticle groups each include at least one metallic nanoparticle capped with at least one polymer, and the metallic layer and the adhesive layer have chemical bonds formed there between.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a surface metallization method and asubstrate having metallized surface manufactured by the same, andpertains particularly to a surface metallization method for siliconsubstrate and a silicon substrate having metallized surface manufacturedby the same.

2. Description of Related Art

Common techniques in silicon substrate surface metallization are, forexample, screen-printing process, hybrid silver contact process, inkjetting process, and vapor deposition process. With the increasing priceof silver, the costs of the above processes have gradually increased.Especially expensive is the vapor deposition process which includes aplurality of steps, increasing the cost, and the metal target used inthe vapor deposition process.

It is generally believed that, one preferred technique in substratesurface metallization is electrochemical plating, which relies on thepresence of a catalyst. For example, in the art of printed circuit boardmanufacturing, the catalyst used in the electroless nickel plating ispalladium tin colloid. However, the surface to be plated must to beetched to form a porous structure before electroless plating, to improvethe adhesion between the palladium tin colloid and the surface of thesubstrate. Therefore, in electroless plating by using palladium tincolloid as a catalyst on the substrate surface having a preferredsmoothness without porous structure, the poor adhesion between thepalladium tin colloid and the substrate surface has become an issue thatneeds to be solved.

SUMMARY OF THE INVENTION

The embodiment of the instant disclosure provides a substrate surfacemetallization method, which utilizes electroless plating for forming ametallic layer on a surface of the substrate, and utilizes the chemicalbonds formed between the surface to be plated that is modified andcolloidal nanoparticle groups to enhance the adhesion between theelectroless metallic layer and the surface of the substrate.

The present disclosure provides a substrate surface metallization methodincluding the following steps. First, provide a silicon substrate havinga surface. Then, modify the surface of the silicon substrate by using atleast one silane compound. Then, deposit a plurality of colloidalnanoparticle groups to the surface of the silicon substrate; thecolloidal nanoparticle groups each include at least one palladiumnanoparticle capped with at least one polymer. Then, electroless platethe surface of the silicon substrate to form an electroless metalliclayer on the surface of the silicon substrate.

The present disclosure also provides a substrate having metallizedsurface. The substrate having metallized surface includes: a siliconsubstrate, an adhesive layer, and an electroless metallic layer. Thesilicon substrate has a silanated surface. The adhesive layer isdisposed on the silanated surface and formed with a plurality ofcolloidal nanoparticle groups. The colloidal nanoparticle groups eachinclude at least one palladium nanoparticle capped with at least onepolymer. The electroless metallic layer is bonded to the silanatedsurface through the adhesive layer. The electroless metallic layer andthe adhesive layer have chemical bonds formed there between.

In order to further the understanding regarding the present disclosure,the following embodiments are provided along with illustrations tofacilitate the disclosure of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a cross-sectional view of a substrate havingmetallized surface during one exemplary fabrication step according to anembodiment of the present disclosure;

FIG. 1B illustrates a cross-sectional view of the substrate havingmetallized surface during one exemplary fabrication step according to anembodiment of the present disclosure;

FIG. 1C illustrates a cross-sectional view of the substrate havingmetallized surface during one exemplary fabrication step according to anembodiment of the present disclosure;

FIG. 1D illustrates a cross-sectional view of the substrate havingmetallized surface according to an embodiment of the present disclosure;

FIG. 2 is a flowchart of a method of modifying a surface of a siliconsubstrate by using a silane compound according to an embodiment of thepresent disclosure;

FIG. 3 illustrates the silicon substrate during the step of modifyingthe surface by using the silane compound and the step of applying anultrasonic vibration according to an embodiment of the presentdisclosure;

FIG. 4 is a flowchart of a method of preparing polyvinylpyrrolidonecapped palladium according to an embodiment of the present disclosure;

FIG. 5 illustrates a colloidal nanoparticle group according to anembodiment of the present disclosure;

FIG. 6 shows test results for physical and mechanical properties of anickel-silicon interface according to an embodiment of the presentdisclosure; and

FIG. 7A and FIG. 7B show results of pull out test for the substratehaving metallized surface formed by using a 50 ppm PVP-Pd solutionaccording to an embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The aforementioned illustrations and following detailed descriptions areexemplary for the purpose of further explaining the scope of the presentdisclosure. Other objectives and advantages related to the presentdisclosure will be illustrated in the subsequent descriptions andappended drawings.

Please refer to FIG. 1A to FIG. 1D for explanation of a substratesurface metallization method according to the present disclosure. FIG.1A to FIG. 1C each illustrate a cross-sectional view of a substratehaving metallized surface during one exemplary fabrication stepaccording to an embodiment of the present disclosure. FIG. 1Dillustrates a cross-sectional view of the substrate having metallizedsurface according to an embodiment of the present disclosure.

As shown in FIG. 1A and FIG. 1B, in the substrate surface metallizationmethod, a silicon substrate 1 having a surface 10 is first provided.Subsequently, the surface 10 of the silicon substrate 1 is modified byusing at least one silane compound, such as aminosilane compound. In theprocess of the surface modification, the amino silane compound having asensitive center for hydrolysis can act as a bridge for the bodingbetween an organic material and an inorganic material, whereby thesurface 10 is modified with the amino functional group of theaminosilane compound. Specifically, the surface 10 of the siliconsubstrate 1 can be modified by a self-assembly monolayer (SAM) processunder room temperature.

To put it concretely, the mechanism of the surface modification caninclude four sections: hydrolysis, condensation, hydrogen bonding, andbond formation. The starting section (i.e. hydrolysis) is therate-determining section, and two of the following sections (i.e.condensation and hydrogen bonding) are spontaneous reactions. In thefinal section (i.e. bond formation), a dewatering process is carried outfor the formation of covalent bonds. For example, the silicon substrate1 can be dewatered by heating (such as heating by an oven at 120 Celsiusdegrees for 30 to 90 minutes) or by vacuuming (for 2 to 6 hours).

The molecular formula of the aminosilane compound used in modifying thesurface 10 of the silicon substrate 1 in the present embodiment is, as aspecific example, (X)3SiY, in which X represents the tentacle forgrafting and Y represents the amino functional group. X in (X)3SiY canbe —OCH3, —OCH2CH3, or —Cl. The amino functional group of theaminosilane compound is the key for the surface modification. Y in(X)3SiY can be olefin, thiol, amine, halocarbon, hydrocarbon, or otherorganic functional group.

After modifying the surface 10 of the silicon substrate 1 by using thesilane compound having amino functional groups (e.g. coating the surface10 of the silicon substrate 1 with a silane layer having aminofunctional groups), molecules with negative charges are easily bonded tothe modified surface 10′ having positive charges. The amino functionalgroups tend to be protonated in an acidic environment, whereby thesurface 10′ modified with the silane compound having amino functionalgroups can have positive charges. Accordingly, the silane compoundhaving amino functional groups can act as a catalyst adsorbed layer forenhancing the adhesion between the surface 10′ of a silicon substrate 1and a catalyst, thus to increase the adhesion between the surface 10′ ofa silicon substrate 1 and an electroless metallic layer.

In the present embodiment, aminosilanes having various numbers ofamino-groups, such as mono-aminosilanes, di-aminosilanes, andtri-aminosilanes, can be applied in the dip-coating process formodifying the surface 10 of the silicon substrate 1. The aminosilanecompound can be 3-aminopropyltriethoxysilane (APS),N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (EDA), or(3-trimethoxysilyl-propyl) diethylenetriamine (DETA).

The structural formula of the APS can be the following:

The structural formula of the EDA can be the following:

The structural formula of the DETA can be the following:

In an exemplary embodiment, the positive charges on the modified surface10′ of the silicon substrate 1 can be provided by the followingamino-groups: ═NH+−, ═NH2+−, —NH3+, and —NH2.

Next, as shown in FIG. 1C, depositing a plurality of colloidalnanoparticle groups to the surface 10′ of the silicon substrate 1 toform an adhesive layer 2. The colloidal nanoparticle groups each includeat least one palladium nanoparticle capped with at least one polymer.For example, the polymer can be selected from the group consisting ofpolyvinylpyrrolidone (PVP), polyvinyl alcohol (PVA), polyacrylic acid(PAA), and any combination thereof.

The palladium nanoparticle in each of the colloidal nanoparticle groupsis capped with the polymer and the colloidal nanoparticle groups eachare attached to the modified surface 10′ with the polymer, such thatchemical bonds are formed between the polymer and the modified surface10′. On the other hand, in the application of a palladium tin colloidcatalyst of the prior art, the palladium tin colloid catalyst isattached to the surface of the substrate merely through the palladiumatoms thereof. In addition, the amount of the colloidal nanoparticlegroups attached to the modified surface 10′ is greater than that in theapplication of the palladium tin colloid catalyst of the prior art.

In an embodiment of the present disclosure, the colloidal nanoparticlegroup can be prepared by a wet process, in which a metallic precursorprotected by a stabilizer is reduced by using a reducing agent. Thestabilizer can be a ligand or a polymer. The size and the stability ofthe colloidal nanoparticle group are related to the synthesis of thestabilizer in the colloidal nanoparticles. Therefore, the stabilizerused in the wet process of preparing the colloidal nanoparticle groupmay be selected according to need. For example, a nitrogen-rich ligandor a water-soluble ligand can be used as the stabilizer protectingpalladium colloidal nanoparticles. The nitrogen-rich ligand can bephenanthroline or sodium sulfanilat. The water-soluble ligand can beisocyanides. The reducing agent used in the wet process of preparing thecolloidal nanoparticle group may be an alcohol, such as methanol,ethanol, propanol, isopropanol, butanol and ethylene glycol.

It is worth mentioning that, the size of the colloidal nanoparticlegroup formed in the wet process can be controlled by regulating theconcentration of the ligand. Using a long chain ligand, increasing theconcentration of the stabilizer, or lengthening the reaction time cancontribute to the formation of the colloidal nanoparticle group having asmaller size.

In the present embodiment, each of the colloidal nanoparticle groupsbonded to the modified surface 10′ of the silicon substrate 1 can be apolyvinylpyrrolidone capped palladium (PVP-Pd) group. In other words,the polyvinylpyrrolidone (PVP) can be used as the stabilizer of thepalladium nanoparticles. The tail end or the ring segment of the PVPpolymer dispersed in a solvent forms a bulky molecule barrier, which caneffectively prevent the aggregation of the nanoparticles.

Compared to the PVP polymers of smaller molecular weights, more PVPpolymers of large molecular weights are attached to the nanoparticlegroup. In addition, the greater the molecular weights of the PVPpolymers attached to the nanoparticle group, the thicker the cappedlayer arranged peripherally around the nanoparticle group. Accordingly,the greater the molecular weights of the PVP polymers, the greater thesize (e.g. diameter) of the colloidal nanoparticle group. The size ofthe colloidal nanoparticle group is related to the molecule weight ofthe PVP polymer, while the nucleation and growth rate are related to thepH value of the solvent, the temperature, and the reducing agent used.The size of the colloidal nanoparticle group is inversely proportionalto the reduction capability of the reducing agent. As a specificexample, the PVP polymer has molecular weight ranging from 5000 to10000, and the colloidal nanoparticle groups each have a diameterranging from 5 nanometers to 10 nanometers.

Next, as shown in FIG. 1D, an electroless metallic layer 3 is formed onthe surface 10′ of the silicon substrate 1 by electroless plating (i.e.autocatalytic plating). The electroless plating relies on the presenceof a catalyst, for example a catalytic metallic layer initially formedon the surface to be plated, which reacts with the metal ions to depositmetal. Alternatively, the surface to be plated itself can be used as thecatalyst for activating.

Usually an electrolytic cell (consisting of two electrodes, anelectrolyte, and external source of current) is used for electroplating.In contrast, an electroless plating process uses only one electrode andno external source of electric current. Although the electroless platingis different form the electroplating, the following describes theoxidation-reduction reaction of the electroless plating in view of anodeand cathode, as shown in the following equations (a) to (f), wherein Rrepresents a reducing agent, Mn+ represents a metal ion, and Mrepresents a metal. The electrons in the oxidation-reduction reactioncome from the oxidation of a reducing agent (equation (b)) or theoxidation of hydrogen (equation (d)).

Anode:Dehydrogenation: RH→R+H  (a)Oxidation: R+OH−→ROH+e−  (b)Recombination: H+H→H2  (c)Oxidation: H+OH−→H2O+e−  (d)

Cathode:Metal deposition: Mn++ne−→M  (e)Hydrogen evolution: 2H2O+2e−→H2+2OH—  (f)

In the electroless plating process, the reducing agent, for examplesodium hypophosphite, formaldehyde, hydrazine, borohydride and amineborane, acts as the anode. The tendency of each of these reducing agentsto be oxidized with respect to various metal ions is different.

It is worth mentioning that, in the electroplating process of thepresent embodiment, the colloidal nanoparticle groups bonded to thesurface 10′ of the silicon substrate 1 can be used as the catalyst foractivating, which reacts with the metal ions to deposit metal on thesurface 10′. The metal deposited on the surface 10′ can act as thecatalyst for the subsequent reactions.

In an exemplary embodiment, the electroless plating is electrolessnickel plating, and the electroless metallic layer 3 formed on thesurface 10′ of the silicon substrate 1 is a nickel layer or a nickelalloy layer. Hypophosphite can be used as the reducing agent in theelectroless nickel plating. At higher temperatures, unstablehypophosphite ion releases hydrogen atoms, which are then absorbed bythe catalyst, for activating the subsequent reactions of the electrolessdeposition for forming the electroless metallic layer 3 formed on thesurface 10′ of the silicon substrate 1.

To sum up, the substrate surface metallization method according to theinstant disclosure utilizes the electroless plating, in which theelectroless metallic layer having a smaller porosity can be evenlyformed on the surface of the substrate. The substrate surfacemetallization method can be applied to substrates having various shapes,for obtaining an electroless metallic layer having a preferred thicknessevenly formed on the surface of the substrate. In addition, thedeposition process can be performed without any electroplatingequipment, which is costly.

The substrate surface metallization method according to the instantdisclosure further improves the formation of the electroless metalliclayer. Specifically, the substrate surface metallization method utilizesthe aminosilane compounds, which are bonded to the surface to be platedand act as the bridge for the connection between organic materials andinorganic materials, to modify the surface to be plated. Moreimportantly, the substrate surface metallization method utilizes thecolloidal nanoparticle groups to form an adhesive layer 2′ on themodified surface 10′, in which chemical bonds (having greater bondingforce than Van der Waals force) are formed between the amino functionalgroups of the modified surface 10′ and the colloidal nanoparticlegroups, whereby the adhesion between the electroless metallic layer andthe surface of the silicon substrate can be increased.

As shown in FIG. 1D, the present disclosure further provides a substratehaving metallized surface. The substrate having metallized surfaceincludes a silicon substrate 1, an adhesive layer 2′, and an electrolessmetallic layer 3. The silicon substrate 1 has a silanated surface 10′.The adhesive layer 2′ is disposed on the silanated surface 10′ andformed with a plurality of colloidal nanoparticle groups. The colloidalnanoparticle groups each include at least one metallic nanoparticlecapped with at least one polymer. The electroless metallic layer 3 isbonded to the silanated surface 10′ through the adhesive layer 2′. Theelectroless metallic layer 3 and the adhesive layer 2′ have chemicalbonds formed there between.

PREFERRED EMBODIMENT

A silicon substrate, such as an n-type silicon wafer doped with p-typeimpurities, is first provided. Subsequently, the surface of the siliconwafer is washed with deionized water. Next, the surface of the siliconwafer to be plated is modified by using aminosilane compounds. Theprocess of modifying the surface can include the following phases: theformation of OH group on the surface, liquid-phase deposition, andbaking. The following describes the process of modifying the surface indetail.

Referring to FIG. 2, which is a flowchart of a method of modifying asurface of a silicon substrate by using a silane compound according toan embodiment of the present disclosure. The silicon wafer is firstimmersed in a solution of 2% hydrofluoric acid for 2 minutes forremoving the oxide layer on the surface of the silicon wafer. Next, thesurface of the silicon wafer is washed with deionized water. The siliconwafer is then immersed in anhydrous ethanol for 5 minutes for surfaceoxidation, in which OH groups can be formed on the surface of thesilicon wafer to be plated. Next, the silicon wafer is immersed in anETAS (3-[2-(2-Aminoethylamine)ethyl-amino]propyltrimethoxysilane)solution. In the ETAS solution, the volume ratio of anhydrous ethanol toETAS is 99 to 1, and the structural formula of ETAS is

The silicon wafer can be immersed in the ETAS solution for 10, 20, 30,or 60 minutes. In a preferred embodiment of the present disclosure, thesilicon wafer is immersed in the ETAS solution for 30 minutes. It isworth noting that, the substrate surface metallization method of thepresent disclosure utilizes the anhydrous ethanol for surface oxidation,thus the surface to be plated can be modified evenly.

Next, the silicon wafer is taken out from the solution and left to dryat room temperature for about 2 minutes to let the solvent remain on thesurface to evaporate for preventing water marks from being generated onthe surface to be plated. The silicon wafer is next placed and baked ona heated plate of 250 Celsius degrees for 10 minutes. Next, the siliconwafer is immersed in an anhydrous ethanol and an ultrasonic vibration isapplied for 10 minutes for removing the aminosilane molecules that arephysically attached to the periphery of the self-assembly monolayer. Thesilicon wafer is then washed with deionized water. Accordingly, the stepof modifying the surface to be plated of the substrate surfacemetallization method is established.

Refer to FIG. 3, which illustrates the silicon substrate during the stepof modifying the surface by using the silane compound and the step ofapplying an ultrasonic vibration according to an embodiment of thepresent disclosure. Before the step of applying the ultrasonicvibration, the aminosilane molecules are stacked in multilayers. Afterthe step of applying the ultrasonic vibration, the thickness of theself-assembly structure is reduced to monolayer.

After the step of modifying the surface of the silicon wafer, thesilicon wafer is immersed in a polyvinylpyrrolidone capped palladium(PVP-Pd) solution. The following describes the process for preparing thePVP-Pd solution. Referring to FIG. 4, which is a flowchart of a methodof preparing polyvinylpyrrolidone capped palladium according to anembodiment of the present disclosure. First, dissolve 0.285 grams of PVP(Poly (N-vinyl-2-pyrrolidone)) in about 44 milliliters of deionizedwater for preparing a PVP solution. The molecule weight of the PVP is8000, and the structural formula of the PVP is

Next, dissolve a precursor, for example 0.329 grams of Pd(NO3)2 havingPd ions, in the PVP solution, such that the color of the PVP solutionturns to brown. A reducing agent, for example 1 milliliter of HCHO, issubsequently added to the PVP solution. Next, 5 ml, 1 N of sodiumhydroxide (NaOH) is slowly added to the PVP solution, such that thecolor of the PVP solution turns from brown to black. Accordingly, thestep of preparing the PVP-Pd solution of the substrate surfacemetallization method is established.

When used, the PVP-Pd solution can be diluted according to need andheated to 40 Celsius degrees. The silicon wafer is then immersed in thePVP-Pd solution. For example, the concentration of the PVP-Pd solutioncan be 50 ppm, 100 ppm, 1250 ppm, or 2500 ppm.

Refer to FIG. 5, which illustrates a colloidal nanoparticle groupaccording to an embodiment of the present disclosure. In the presentembodiment, the colloidal nanoparticle groups each have a diameter of 5nanometers. The arrangement of the Pd nanoparticles and the PVPmolecules in each of the colloidal nanoparticle groups is similar tothat of ZnS and the PVP molecules act as protecting agents. As shown inFIG. 5, the Pd nanoparticles are capped with the oxygen atoms of the PVPmolecules. It is worth mentioning that, the greater the concentration ofthe colloidal nanoparticle group solution, the more colloidalnanoparticle groups bonded to the surface of the silicon wafer, and thegreater the sizes of the colloidal nanoparticle groups bonded.

Chemical bonds can be formed between the colloidal nanoparticle groupsand the modified surface having amino functional groups. In addition,the colloidal nanoparticle groups bonded to the surface of the siliconwafer can be used as the catalyst for activating in the electrolessplating, whereby the adhesion between the surface of the silicon waferand the electroless metallic layer formed therein is enhanced.

Next, electroless plating is carried out for forming the electrolessmetallic layer on the surface of the silicon substrate. Specifically,after taken out of the colloidal nanoparticle group solution and washedwith deionized water, the silicon wafer is immersed in the electrolessnickel plating solution (9026M Electrodes Nickel) provided byOMG(Asia)Electronic Chemicals Co., Ltd, Taoyuan County, Taiwan. As aspecific example, the silicon wafer is immersed in the electrolessnickel plating solution for 5 seconds to 180 seconds, at 80 Celsiusdegrees, pH 4.9. Accordingly, the step of electroless plating thesurface of the silicon substrate of the substrate surface metallizationmethod is established.

By a scanning electron microscope, the growth of the film thickness ofelectroless nickel deposition can be observed. The greater theconcentration of the colloidal nanoparticle group solution (e.g. PVP-Pdsolution) used, the more the electroless nickel-phosphorus alloyparticles formed at the interface of the silicon wafer and the platinglayer, and the greater the sizes of the electroless nickel-phosphorusalloy particles. The plating rate is not directly related to theconcentration of the colloidal nanoparticle group solution used. In anexemplary embodiment, in the electroless deposition for forming a nickellayer having a thickness of about 200 nanometers on the silicon wafer,the deposition time can be controlled in substantially one minute.

The following describes the tests performed for physical and mechanicalproperties of the surfaces of silicon substrates metallized according tothe above embodiment and other embodiments. Referring to FIG. 6, whichshows test results for physical and mechanical properties of anickel-silicon interface according to an embodiment of the presentdisclosure.

The tests are carried out by the standard test method ASTM D4541 forpull-off strength of coatings using portable adhesion testers. First,each of the test pieces (e.g. the substrates each having metallizedsurface) is adhered to a glass substrate by a large amount of epoxyresin, and a dolly (which has a diameter of 10 mm) is adhered to thesurface to be tested by epoxy resin. Each of the test pieces adheredwith the glass substrate and the dolly is left for 3 hours and thenbaked in an oven for 2 hours at 70 Celsius degrees. After the testpieces are taken out of the oven and left to cool. A pull-off strength(commonly referred to as adhesion) of the plating layer of each of thetest pieces is obtained by using an adhesion tester. The siliconsubstrate of the test piece 1 is formed with a surface to be platedhaving commercial tin colloid palladium catalysts attached thereto. Thesilicon substrate of the test piece 2 is formed with a surface to beplated, which is firstly modified by using ETAS and then catalyzed byusing commercial tin colloid palladium catalysts. The silicon substrateof the test piece 3 is formed with a surface to be plated, which isfirstly modified by using ETAS and then immersed in a 50 ppm PVP-Pdsolution. The silicon substrate of the test piece 4 is formed with asurface to be plated, which is firstly modified by using ETAS and thenimmersed in a 100 ppm PVP-Pd solution. The test results are shown inFIG. 6 and listed in the following chart.

test piece Average adhesion (MPa) test piece 1 2.57 test piece 2 5.36test piece 3 10.6 test piece 4 11

As shown in the above chart, the adhesion of the plating layer of thetest piece, which is formed by the process including the step ofmodifying the surface to be plated by using ETAS and the step ofdepositing a plurality of PVP-Pd groups to the surface to be plated, isimproved, compared with that of the test piece. Especially, comparingthe adhesion of the plating layer of the test pieces 1 and 2, which areformed by using commercial tin colloid palladium as catalyst, it isworth noting that, the adhesion of the plating layer of the test piececan be improved by modifying the surface to be plated by using ETAS.Furthermore, as shown in FIG. 6, the standard deviations of the testpieces 3, 4, which are formed by using PVP-Pd, are greater than those ofthe other two test pieces.

Particularly, the cleavage planes of the test pieces generated duringthe pull-out tests may have different configurations. Referring to FIG.7A and FIG. 7B, which show results of a pull out test of the substratehaving a metallized surface formed by using a 50 ppm PVP-Pd solutionaccording to an embodiment of the present disclosure. FIG. 7A and FIG.7B show two different configurations of the cleavage plane of the testpiece, which is formed by the process including the step of modifyingthe surface to be plated by using ETAS and the step of depositing aplurality of PVP-Pd groups to the surface to be plated by using a 50 ppmPVP-Pd solution. In the configuration shown in FIG. 7A, the Ni layer isentirely separated from the silicon surface. That is, the cleavage planeis generated via an out-of-phase separation. In the configuration shownin FIG. 7B, the silicon substrate is fragmented, which results from thelarge adhesion force in parts of the Si-Ni interface, and some of thecleavages are generated within the silicon substrate via an in-phaseseparation.

In the cases where the Ni layer is entirely separated from the siliconsurface, the adhesion of the plating layer of the test piece, which isformed by using a 50 ppm PVP-Pd solution, is 6.44 MPa; the adhesion ofthe plating layer of the test piece, which is formed by using a 100 ppmPVP-Pd solution, is 8.47 MPa. In the cases where cleavages are generatedwithin the silicon substrate via an in-phase separation, the adhesion ofthe plating layer of the test piece, which is formed by using a 50 ppmPVP-Pd solution, is 13.73 MPa; the adhesion of the plating layer of thetest piece, which is formed by using a 100 ppm PVP-Pd solution, is 13.54MPa.

To sum up, the substrate surface metallization method provided by thepresent embodiment utilizes electroless plating to replace the silverscreen printing, copper plating, or nickel plating, in order to reducethe cost. Especially, the substrate surface metallization methodutilizes aminosilane to modify the surface to be plated and utilizesPVP-Pd to form chemical bonds, which enhancing the adhesion between theelectroless metallic layer and the silicon surface. The entire processof the substrate surface metallization method is a wet process, which issimplified. The cost can be reduced compared with the chemical vapordeposition process of the prior art, and the yield rate is promoted atthe same time.

The descriptions illustrated supra set forth simply the preferredembodiments of the present disclosure; however, the characteristics ofthe present disclosure are by no means restricted thereto. All changes,alterations, or modifications conveniently considered by those skilledin the art are deemed to be encompassed within the scope of the presentdisclosure delineated by the following claims.

What is claimed is:
 1. A substrate having metallized surface, comprising: a silicon substrate having a silanated surface; an adhesive layer disposed on the silanated surface, wherein the adhesive layer is formed with a plurality of colloidal nanoparticle groups, the colloidal nanoparticle groups each include at least one metallic nanoparticle capped with at least one polymer; and an electroless metallic layer bonded to the silanated surface through the adhesive layer; wherein the electroless metallic layer and the adhesive layer have chemical bonds formed there between.
 2. The substrate having metallized surface of claim 1, wherein the electroless metallic layer is a nickel layer or a nickel alloy layer.
 3. The substrate having metallized surface of claim 1, wherein the silanated surface has a silane layer having at least one amino functional group.
 4. The substrate having metallized surface of claim 3, wherein the amino functional group has one to three amino-groups.
 5. The substrate having metallized surface of claim 1, wherein the polymer is selected from the group consisting of polyvinylpyrrolidone, polyvinyl alcohol, polyacrylic acid, and any combination thereof.
 6. The substrate having metallized surface of claim 1, wherein the structural formula of the polymer is


7. The substrate having metallized surface of claim 6, wherein the metallic nanoparticle is capped with an oxygen atom of the polymer.
 8. The substrate having metallized surface of claim 6, wherein the polymer has molecular weight ranging from 5000 to
 10000. 9. The substrate having metallized surface of claim 6, wherein the colloidal nanoparticle groups each have a diameter ranging from 5 nanometers to 10 nanometers. 